How far away is the Devonian?

The Woodstock Times – On the Rocks; Feb. 15, 2018

Robert and Johanna Titus

   If you have been longtime readers of “On the Rocks” then you will know that we almost always write about geology that we have gone out to the field and seen for ourselves. We would like to depart from that in this issue. In fact, we are going to step out of Geology, itself, altogether. It all began when we were pondering the Devonian time period. That’s the geological chapter that extended from 419 to 359 million years ago. It’s an important unit of time here in the Catskills. All of the bedrock you see hereabouts was formed during the Devonian.  But what, we wondered, was going on in the universe that surrounded the Earth during that time? That got us pondering some more. We were being typical scientists and we were doing typical science thinking.

We realized that when you are looking into space, you are always looking into the past. When you are looking at the moon, you are looking at an image of light that departed it a short time ago. We asked our cell phone, and it told us that the image of the moon, that we see, left it 1.3 seconds ago. Our cell phone went on to tell us that light from the Sun is Eight minutes and 20 seconds old. We can’t actually see the Moon or the Sun; we can only see them as they were in the past. Do you think thoughts like this? Then you are a bit of a scientist.

We realized that there must be something out there that emitted light during the Devonian, but our cell phone was of no help. Our “smart” phone might have been stumped, but the Physics department at Hartwick College was not. We posed our question, by email, to the faculty of that department and in just a few minutes we got a very good answer. Living, breathing PhD physicists do these things all the time; they are very bright people. Dr. Kevin Schultz, Associate Professor of Physics, looked into NASA records and found a galaxy, poetically named UGC 12591. It lies just a little less than 400 million light years away from our Earth. That makes its light just a little less than 400 million years old. That light has been traveling toward the Earth all that time. When it reached the halfway point, Dinosaurs were just getting themselves started (that’s more science thinking). In short, that galaxy’s light was shining during the Devonian; it was there during the Devonian.

Would you like to see this Galaxy? Well, you need to look into the westernmost region of the Pisces-Perseus Supercluster. That is an enormous chain of galaxy clusters which extends across some 250 million light years of space. It is regarded as one of the largest “things” found in the cosmos. UGC 1259l is big; it is four times the size of our Milky Way Galaxy. That makes it four times bigger than everything you can see in the night sky. Think about that for a moment. The bad news is that you won’t be able to actually look at UGC 12591; it’s too far away. Our photo was taken by the Hubble Space Telescope. If you don’t have access to the Hubble, you won’t be able to see it yourself.

That galaxy is out there; it is that far away. But Hubble is not just looking far into space; it is looking far into the past. This column’s photo is of the galaxy as it was when lower Devonian tropical seas were invading New York State. Our local limestones are as old as the image you see in this column. That light was in transit while the trees of the fossil Gilboa Forest were growing. That light was geologically ancient at the very times when all the rocks you see around here were forming. We scientists ponder such things.

We should specify that we are not that smart; we paraphrased much of this article from a NASA publication. Dr. Schultz helped. We hope that Bob Berman will forgive our trespassing.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.” Read their blogs at “thecatskillgeologist.com.”

What is in limestone?

Windows Through Time; The Register Star

Robert and Johanna Titus

Last week we introduced you to a special type of rock– the fossiliferous limestone. It is largely composed of fossil shells and fragments of fossil shells. We showed you a very fine example of a shelly limestone, something called the Glenerie Limestone. It is exposed in an outcropping along Rte. 9W, south of the bridge at Glenerie. It is simply an extraordinary rock, absolutely packed with marine shellfish fossils. It is so much fun to explore an outcropping like this.

But how was it, exactly, that a pile of broken shells turned into a rock? That’s an important question. But how can we answer it? After all, nobody was there while it was hardening. Nobody saw it happening. And what can you learn from just looking at such a limestone rock anyway? These might seem like tough questions, but let’s tackle them today.

Turns out that there are different ways of looking at a limestone. One way is to make something called a thin section. That is a slice of rock so thin that you can look right through it. But now, still another question, how do you make such a thing?

You start by cutting your piece of limestone in half. Pretty much every geology lab has a rock saw. It has a turning blade that slices right through rock. You cut your rock into two small pieces and then you pick one and grind it down to a smooth shiny surface. And pretty much any geology lab can do that. We put grits onto a large piece of plate glass and grind the rock. When it is smooth enough, we cement it to a small slide of glass. We cut as much as possible off the limestone so that there is a relatively thin sheet of rock cemented to the glass. If this is done right, and it takes practice, you will already be able to see through the rock. But there is more that needs to be done.

In fact, now comes the hard part. We go back to that plate glass, clean it, and sprinkle it with a very fine grit. Then we grind, and grind, and grind. That bit of limestone keeps getting thinner. And, with practice, geologists can make it very thin. Then a sheet of cover glass is cemented onto it and the result is (drum roll) a thin section! You take it to a good microscope and now you can look right into the rock.

And what you can see is its innards. Take a look at our photo. It shows a thin section view from a piece of Ordovician aged limestone called the Trenton Limestone. One of us (Robert) spent 25 years studying this unit and its fossils. What you see are cross section views of several fossils. On the right center you will see a piece of a creature called a trilobite. We have written about trilobites in Windows Through Time several times. They are marine creatures that might remind you a little of horseshoe crabs. This is a thin section view of one of the creature’s skeletal elements. See the white holes in it? Those housed sensory hairs in life. In the upper left center and lower left there are fragments of crinoid skeletons. Again, we have written about these distant relatives of starfish.

There are several smaller bits of fossil debris in this view. It’s a good image; it shows just how abundant shell fragments are in a limestone. Few of these would be visible to the naked eye so this thin section image is important.

The rest of the view is all white; what is that? It’s cement. It’s a mineral called calcite which is calcium carbonate (CaCO₃). That’s the stuff that “glues” all the other grains together to turn the whole thing in a rock.

Calcium carbonate is a very soluble mineral and there is a lot of it in sea water, especially in tropical seas. It readily crystalizes and can quickly, by geological standards, harden a limestone. All those shell fossils are also composed of calcium carbonate and that means that nearly everything you see in this thin section view is CaCO_3.  Calcite reacts with hydrochloric acid; it effervesces, sometimes very actively. Many geologists carry an eye dropper, filled with this acid, into the field. If they think they have limestone, but are not sure, they just do the “acid test” and see. This acid is marketed as muriatic acid and you can get some and test rocks yourself.

Thin section analysis is hard work, so we don’t recommend that you learn, but we hope you enjoyed reading about it.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

What is a limestone? Pt 1

Windows Through Time; The Register Star

Updated by Robert and Johanna Titus

Like most people, you have very likely heard the word “limestone.” We use the word frequently in our columns. But do you really know what a limestone is? If you saw one, could you identify it? If not, then let’s go to work and fix that. Let’s learn about one type: a “fossiliferous limestone.”

Limestone is one of the most commonly found types of stratified rock. Stratified means that the rock is layered; it is composed of strata. When you look carefully at a limestone, you are likely looking at a slab of the rock. That slab was originally part of a single stratum. The rock broke up along the surfaces of that stratum to become a loose chunk of rock. When you are looking at such a limestone you are likely looking at the surface of that stratum. And, you are, therefore, looking at a small bit of an actual ancient sea floor. This stratum had been deposited as a sheet of shelly sediment on the bottom of that ocean. That sediment was composed of a large number of shells and shell fragments. These, of course, are now fossils. The sediment in between those fossils is likely to be largely composed of smaller shell fragments. Many of those had been ground down into sediment. That sediment can be sand sized stuff, or even finer. Each grain of sand was once part of a shell. You can’t recognize that anymore, but that is still how it got its start.

That stratum was deposited and then, later, it was buried under more and then even more strata. The limestone sediment piled up and the weight of it helped begin the processes that would harden it into rock. So, any slab of fossiliferous limestone has quite a past. It had once been a soft sediment, lying on the floor of an ocean, but all that has passed; now it is a rock.   A very large percent of this rock was once shell material. It could be 100 % but it has to be about 60 to 70% or the rock does not qualify as a limestone.

So, identifying a fossiliferous limestone should be simple. And most of the time it is. Take a look at our photo. It’s a close-up of what is called the Glenerie Limestone. (Yes, it is from the village of Glenerie.) It is a Devonian aged limestone, like so many of them around here. The images that leap out of the photograph are the fossils. The one on the left center is a brachiopod, a bivalved invertebrate animal. It’s called a bivalve because it has two shells. That’s just like a clam, but this is not a clam; it is an entirely different creature.

This brachiopod is a full specimen; all parts of both shells are present. It was never broken up.
This specimen is surrounded by fragments of other shells, most of which had also been brachiopods. This rock is an excellent example because, if you could see the original, you would see progressively smaller and smaller shell fragments. It is easy to guess that every particle in this rock was once part of a shell. And that, in fact, is the case. This is a classic fossiliferous limestone. We look again and we realize that we are looking at a small stretch of a Devonian sea floor.

But, can we say more about that ancient sea floor? We sure can, Geologists like to study the modern world. There is so much out there that can help us understand the past. We like to go out and find locations where such limestones are forming today. We have been doing so for centuries and we always find the same thing. Fossiliferous limestones always form on the bottoms of shallow tropical seas. The Bahamas are a terrific example of such a place.

Our Catskills once, about 400 million years ago, lay about as far south of the equator as today’s Bahamas are north. In short, the Glenerie Limestone formed in a Bahamian seafloor setting. We have both been to the Bahamas and so we know exactly what that setting looked like. When we visit the Glenerie Limestone, along Rte.9W in Glenerie, we envision that Bahamian setting.

We don’t even have to close our eyes. We are standing on the soft pink sands of a tropical sea. All around us is that sea floor. And, all around us, are clear aqua-colored waters. Above us, but only about 20 feet up, we see waves passing by, driven by tropical breezes, we see the sunlight sparkling off the passing wave crests. What do you see along Rte. 9W?

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Bend in the Road

On the Rocks, The Woodstock Times

May 13, 1999

Updated by Robert and Johanna Titus

As geologists there are so many places for us to visit, but we find that there are also some places that we return to over and over again. One of those is the hairpin turn in the road at Plattekill Creek. It’s exactly 1.2 miles above the bottom of the canyon road. When you get there, you will find a very sharp right turn. The road then goes around another broader left bend and continues up the canyon for another mile until reaching the top.

The bend in the road is just one of those places where we see all sorts of things. First there is an especially fine view. Look west and you see the whole canyon before you. Look back to the southeast and you get a nice peak at the Hudson Valley. At night you can see the Rhinebeck Bridge and part of Kingston. Look west at night and, depending on the moon and the weather, you get all sorts of silhouette effects on the horizon.

But it is the bedrock geology that we would like to talk about today. A lot of rock had to be cut through and carted off to make way for the road and that has provided us with a fine outcrop. Just before the bend you will see about 40 feet or so of massive sandstone. That is the cross section of an ancient river. we, of course, really mean it when we say ancient. We are talking about the Devonian time period, about 385 million years ago. There was a river here then and it flowed across a vast floodplain. This ancient stream had nothing to do with today’s Plattekill Creek; it is just a nameless river, lost in the annals of Earth history. The river itself was prone to times of high and active flow. If you look at the strata here, you will see the evidence: Steeply inclined strata called cross beds. In our mind’s eye, we envisioned days when very powerful flows of water had passed by here.

Above the river deposit there are five feet or so of red shales. These are old floodplain sediments; they were deposited during the floods that occasionally swept through here. The red color fades at the top in what is an old soil profile. It’s only five feet of red strata, but what a record of time! These sediments record untold numbers of floods and the long slow process of soil formation.

As you round the bend in the road you find another ten feet or so of river sandstones. We look at rivers today and think of them as permanent landscape features, but they are not. Floodplain rivers come and go; they slowly meander back and forth, snake-like, across the flat lands. A river will occupy a site for a long time, then meander off, and much later, it may meander back. Or maybe some other river will meander into the same site. That’s what you see at the bend in the road. First there was one river, then a red floodplain, and then the same or another river returned to this site.

Continue up the road and then you will see that there is still another five feet or so of red floodplain with the paleness of another fossil soil. Above that is the single best geological feature of the site. That second red floodplain is followed by a truly massive river sandstone. There must have been a very large river here, one that deposited a lot of sand, about 50 feet or more. But it is right at its base that we found the best feature. The sandstone has eroded an overhang above the softer red shales. Look under and up at the sandstone and you will find what we call “drag marks.” Drag marks are just that. Something, probably a waterlogged tree trunk, was dragged down the stream by the river currents. It dragged into the muds and left the mark. Actually, there are two of them. They represent just the few seconds it took for a log to move along and leave the drag mark. But those few seconds have been recorded there in the rock, for nearly 400 million years.

The bend in the road is an especially nice exposure of some very typical Catskill stratigraphy. If you spend a little time here and work your way through the site’s stratigraphy you will learn a lot about our area rocks, and it’s not very complex. Basically, the light sandstones are river channel deposits, and the red shales are old floodplain sediments. You can apply what you have learned here, throughout most of the Catskills. That’s a lot of knowledge.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

THE CATSKILL GEOLOGISTS BY PROFESSORS ROBERT AND JOHANNA TITUS

A Book about the fossil Gilboa Forest

Our Catskills can hardly be portrayed as being a great center for scientific studies; there are no great research universities here, nor any high-powered labs. But these mountains are known all around-the world for one enormously important scientific fact. The Catskills are home to some of the oldest known examples of forest ecologies. We mean not just fossil trees but actual fossilized forest ecologies. Our Catskill Mountains are essentially a petrified delta. It’s called the Catskill Delta from the Devonian time period of about 420 to 360 million years ago. The strata of our mountains, here and there, display patches of what can be called the Gilboa Forest, an assemblage of very early and very primitive trees. With them are the weeds, bugs and fish that lived on the soils and in the rivers of that delta. It is an enormously important record of a critical chapter of evolution, when life was moving out of the oceans and onto the land

Sadly, the scientific literature about the Gilboa Forest has almost always been written in a nearly impenetrable technical prose. Now, at last., three of the today’s principal researchers have put together a book aimed at introducing the Gilboa Forest to the people of the Catskills: “The Catskill Fossil Forest.” These authors, Binghamton University professor William Stein and State Museum geologists Helen Van Aller Hernick and Frank Mannolini, feel an obligation to the people of the Catskills to explain their science. The book, published by the Gilboa Historical Society Press, is an account of recent studies of fossil forest in Gilboa, Cairo and South Mountain in the eastern Catskills. We learn of the step-by-step uncovering of these three important fossil sites and are introduced to the major categories of fossil trees that were brought to light. The book is brief and extremely well illustrated. It is a most unusual and remarkable effort by professional scientists to explain their work to the local community. It is expected to be introduced at a book signing between 11:00 and 4:00 at the Juried Museum in Gilboa on Sunday. June 12^th.

But, while aimed at the general public, this is indeed a book of science. You need to know how to read it. First, this is not a novel; you just don’t start at the front and read through it, cover to cover. In fact, you might begin by spending a fair amount of time looking at the illustrations, especially those of the different fossil trees. Look them over and read the legends. Much of science is communicated through illustrations so you can learn a lot from this. You can also start picking up the Latin terminology and that will prepare you better to read the main text. After all, if you are going to be reading about Pseudosporochnalean and Eospermatopteris trees, then it really helps to have the right images in your mind. And there’s another big plus, you’re going to feel so incredibly smart knowing these words and so many others. All this may be tough at first, but you can do it.

And then there are the insets. The authors have picked out a large number of special subtopics for special readings, separate from the main text. They are important and often quite interesting. Each is a separate bit of education. You should spend time just browsing these.

We strongly recommend this book. If you enjoy our columns, then you will certainly want to learn what is presented in this account. It’s important science. Local science.

It is available at the Gilboa Museum gift shop and at local bookstores. Online at gilboafossils.org/store-home/

Contact the authors at randjtitus@prodigy.net. Join their facebook page The Catskill Geologist. Read their blogs at “thecatskillgeologist.com.”

The Reasons for Seasons

Stories in Stone; The Columbia County Independent

Updated by Robert and Johanna Titus

Our Hudson Valley region summers generally bring wonderful weather with dry air and cool nights. Our autumns are spectacular with their foliage. Our winters are dreadful, and once again it is that time of the year. We stoically accept the onset of another cold season and make do with the holidays as some sort of compensation. Few of us, however, know or even wonder why we must endure this annual season. Do you? Some of you might be able to give a reasonably good explanation for our winter season in terms of the Earth’s orbit about the Sun. Many of you, however, might flub the story; it is just a bit complex.

But it really doesn’t matter; We are not interested in the standard astronomical explanation of winter. We would like to consider a deeper reason, in fact, the real reason it is cold out there right now, and that has less to do with the Earth’s orbit than it does with the what’s right above you, or rather, what is not right above you. Read on:

Even if your astronomy is not very good, most of you can probably run through a quick description of the greenhouse effect, it’s one of the leading environmental fears we face today. Briefly, our world’s industries are burning fossil fuels and pumping out large volumes of carbon dioxide into the atmosphere. Carbon dioxide traps solar energy in our atmosphere much the way the glass traps solar energy in a greenhouse. As industrial production of carbon dioxide continues, it may be that the Earth’s climate will warm up with all sorts of unfortunate side effects. Such a fate is sometimes referred to as the “Greenhouse Earth.”

But what if it were the other way around? What if the quantities of carbon dioxide were declining instead of increasing? That gets us to a term which is rarely used – the “Icehouse Earth.” That’s a notion few have been much worried about nowadays, but it actually has happened, and that gets us back to what isn’t above you. In earlier columns we wrote that there were, in the distant past, great mountains towering above our Columbia County region along with most of western New England. These mountains are called, by geologists, the Acadians. They should not be confused with today’s small Taconics and Berkshires; these mountains rose to elevations of tens of thousands of feet and that was right here. That was during the late Devonian time period or about 375 million years ago.

This had been a time when the world was truly a Greenhouse Earth. There was actually 16 times as much carbon dioxide in the Devonian atmosphere as is today. That greenhouse effect must have been enormous; tropical climates prevailed across the planet. But it was not to last. Here in today’s New England, our rising Acadian Mountains were subject to chemical weathering and erosion. Those processes converted the Acadians into sediment which, eventually, hardened into rocks deposited across the rest of New York State. What is critical here is that the processes of chemical weathering consume carbon dioxide; they take it right out of the atmosphere. As the Acadians weathered away, the amounts of carbon dioxide in the atmosphere dropped dramatically, from 16 times as much as today down to merely today’s levels by the end of the Devonian Period, about 350 million years ago. This, as you might guess, resulted in a reversal of the greenhouse effect and quite a cooling of the climate. In fact, there was an early ice age at the end of the Devonian.

There is plenty we don’t understand about this story, but this was a turning point in Earth history. Carbon dioxide would never again be as abundant as it was during the early Devonian. Its levels would rebound again during the age of the dinosaurs and those great hairless monsters certainly must have enjoyed the temporary restoration of the greenhouse warmth. But there simply would never again be so much carbon dioxide, and the climate would slowly deteriorate, with cooling temperatures, especially during the last 60 million years. Some argue that this cold is what caused the extinction of the dinosaurs. There is a good case that can be made for this argument too. Winters, which probably had not been much of a problem during the early Devonian, slowly became longer, colder and more distinct from the rest of the year. Thus, what we know as seasons made their appearance. The process has continued right into our time. In reality, even if industrial pollution continues unabated, ours is a time of an Icehouse Earth. Glaciers in Antarctica and Greenland attest to that.

So, were our old Acadian Mountains responsible for winter? Well, that’s a bit of a stretch, but it is fair to say that the many processes that came to produce and then destroy the Acadians were all part of a climate machine that eventually created the Icehouse Earth climate that we can look forward to for the next three or four months.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “Tye Catskill Geologist.”

Roeliff Jansen Kill, Part 6 –Bottom of a lake

Stories in Stone

Updated by Robert and Johanna Titus

We continue our journey down the Roeliff Jansen Kill. Last time we had reached the village of Elizaville and there we found an ice age delta. Back, about 14,000 years ago, the Roeliff Jansen Kill had reached the shores of an ice age lake. It’s known to geologists as Glacial Lake Albany. For quite some time that lake represented the downstream end of the Roe-Jan and, as the river flowed into the lake, it deposited the sediments of the Elizaville Delta.

But the lake was doomed; all lakes are. Lakes are ephemeral features; time will always bring their destruction. The waters of Glacial Lake Albany eventually drained down the Hudson and into the Atlantic Ocean. That left behind a big empty basin with the Roe-Jan flowing into it.

Now the Roe-Jan tumbled over the edge of its old delta and reached the flats of the old lake bottom. This constitutes a whole new stretch of the river, and we can, of course, explore that stretch. We can see it with or without the lake waters.

From Elizaville, take County Rte. 19 north. You will soon cross a small creek and then see a large apple orchard. Just beyond the orchard, the road will cross another small creek and then start to climb uphill a bit. You have just crossed Doove Kill and are now rising up onto the Manorton Delta. Doove Kill, just like the Roe-Jan, flowed into Lake Albany and created its own delta. On the left (west) side of the road you will see a small pond. That is an old ice age pond. It formed just like Twin Ponds at Elizaville. A large block of ice was buried in the delta and, when it melted, it left behind the hole in the ground that became a pond.

What we are doing now is driving north, parallel to the shores of what had been the old lake. Look to your left and imagine the waters of Lake Albany stretching out before you. The first 50 or 100 feet of lake are covered with a thin sheet of ice. Beyond that are the open waters of the lake. There are a number of small islands out there, but it is, otherwise, a very big lake. The other side of Lake Albany is nine miles away. You can see Mount Marion rising above the western shoreline. When we look north and then south, we see the lake disappearing into the horizon; it is, indeed, a very large lake!

But we have exploring to do. We continue driving north on Rte. 19 until we reach the village of Manorton. There we take a left fork and follow County Rte. 8 off to the northwest. We begin a long steady descent and drop down from and elevation of 260 feet to one of 190 feet. We are dropping off of the Manorton Delta and our descent is a journey into the depths of Lake Albany.

Imagine the waters deepening around you as you drive down the road and imagine it growing darker as well. Our journey takes us about a mile and a half until we get to the village of Blue Store. That’s a historic old town, but out trip is taking us well beyond what most people reckon as history. We arrive at the old hotel and restaurant and look around. The countryside here is flat and expansive; it is the floor of the lake.

It is always somewhat startling to see a flat landscape and recognize it as an old lake bottom. We are now 70 feet beneath the waves of Lake Albany. This is not a nice place to be; the water is murky and it is dark and very cold here. But, like or not, this is Blue Store as it was, about 14,000 years ago. Once again, the Roe-Jan has made us time travelers.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

Roeliff Jansen Kill, Part 5: Twin Lakes

Stories in Stone

Updated by Robert and Johanna Titus

The Roeliff Jansen Kill is certainly not one of the world’s great rivers; in fact, it is not much more than a run-of-the-mill creek. But this is the fifth article that we have written about the Roe Jan. We picked it up near its source and have been following it downstream, tracing its journey to the Hudson River. Each of our first four installments has revealed an entirely different facet of the kill. Each segment of the creek has brought to light a separate geological “personality.” That’s remarkable and we are only just past the halfway point!

Last time we had arrived at Elizaville. There we found that the Roe-Jan had emptied into what is known as Glacial Lake Albany. That was an expanse of cold water that spread across much of the Hudson Valley at the close of the Ice Age. We ended up standing along Hapeman Road, realizing that we were at the bottom of a 60-foot-deep ice water lake.

We can begin this episode where we left off. Gaze up those 60 feet and appreciate that you are on the floor of an old lake. At noon, on a late ice age day, you could have looked up here and seen the sunlight playing upon the passing waves. Occasionally cakes of ice, mini-icebergs, would drift by, swept along by the wind. To be a geologist is to be able to plant each of your two feet firmly in different moments of time and we can really do that here. Look off to the west; we see one of your feet on today’s flat landscape and then also see your other foot standing upon the dark still, muddy bottom of a lake. What of this, exactly, is imagination and what, exactly, is real?  And where are the boundaries of the imagined and the real? To be a geologist is to experience such things.

But we must continue. Drive back east on Hapeman Road and arrive at a good vantage point to see one of the two “Twin Lakes” that are here. Elizaville is perched upon a very fine plateau, one which we have seen was once a delta. With good drainage and lying well above any flood threats, this was a logical place to build a village. But it was the two lakes that most attracted people here. They have built homes around the shores of the lakes because people just like living on shores.

But what is the story of these lakes? How did they come to be? Those are the sort of questions that a geologist loves to answer. The two lakes take us back to the time of the Elizaville Delta. We must imagine the time when the Roe Jan was actively flowing into Glacial Lake Albany. The word “actively” probably does not do justice to what was going on here; enormous amounts of meltwater were raging down the Roe-Jan, and, loaded with dirty sediment, pouring into the lake. Much of that sediment was being added to the growing delta, but there was a problem.

The shoreline area of the lake is likely to have had a lot of floating ice running along it. As sediment was deposited in the lake shore vicinity, a lot of that ice would have come to be buried. Sediment is very good insulation so this buried ice might well have lasted for centuries, but eventually it would melt. As masses of shoreline ice did melt, the sediment above would have collapsed and that would, in each case, leave a large hole. That is what happened at Elizaville, not once but twice.

The result is something called an “ice-cored delta” and these are common in New York State. We frequently find a perfectly good ice age delta with one or, in this case, two holes in it. If the holes are not very deep then they are just swales in the landscape, pretty but not very important. But if they are deep enough then they will fill with water and form lakes or ponds. If they are very big, then people will settle along their shores and maybe put boats into the water. In any event, geologists will always come along and admire these emblems of the Ice age.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

The delta of a river

Stories in Stone

Updated by Robert and Johanna Titus

We continue our journey down the Roeliff Jansen Kill. We began back at Bash Bish Falls and now we have arrived in Elizaville. The kill had been flowing southeast all this distance and had even crossed into Dutchess County. But now, curiously, it has turned sharply to the northwest and is heading towards its destination, a confluence with the Hudson River. But we are going to pause and focus today on the village of Elizaville. There is something special there.

Elizaville lies perched on a bluff that rises above the Kill just to its north. Much of the village is composed of houses built on the shores of the two lakes that are found in the center of the town. They are called, logically enough, “Twin Lakes.”

We have been traveling west on Route 2 and, as we enter Elizaville, we turn right and head north into the village. The road passes between the two lakes and quickly we turn left onto Hapeman Road and head west. Soon it drops down a steep slope, turns left and merges with a Pleasant Vale Road. This part of Hapeman Road has a lot of storytelling to do.

Pull over anywhere along Hapeman, get out and look around. Right along the east side of the road there is a very fine, and very steep slope rising, even towering above the road. Elizaville is built upon the bluff that is defined by the top of that slope. Almost all Hudson Valley geologists would recognize this feature; it is an ice age delta. Back at the close of the Ice Age, just after the glaciers had melted north and the valley was opening up again, something happened. A vast lake was left behind by the retreating glacier. There was, of course, a lot of meltwater, but there was something else. The crust of the earth here had been pressed down by the weight of the ice.

Off, a hundred miles or so to the south, the crust had already rebounded from a similar compression. But here in Elizaville the crust was still depressed. That meant that there was a basin just behind the retreating glacier, and that basin was filled with meltwater which formed what is known as Glacial Lake Albany. The Roeliff Jansen Kill would flow into Lake Albany. Today’s Elizaville marked the end of the river back then. Like any river flowing into any body of water, the Roeliff Jansen Kill would deposit the sediments of a delta.

Deltas form all over the world. They form where great rivers flow into oceans or where small brooks flow into ponds. They can be very large or very small. And it really doesn’t matter; in the end they all have the same morphology, or geomorphology if you prefer. All deltas are composed of sediment which has piled up to about the level of the waters. A very large delta will see sediments rise to just above water level. Thus is formed a broad flat surface called, by geomorphologists, a “topset.” Most of Louisiana is topset and so too is most of Bangladesh. Both regions are flat and rise just barely above sea level. The village of Elizaville is perched upon the topset of the Elizaville Delta.

Beyond the topset all deltas display steep slopes. Sediment, which had been carried across the topset, came to the outer edge, and tumbled down a slope. That’s how the foreset slope came into existence. Over time, the foreset will accumulate more and more sediment and advance towards the center of the lake. That makes the delta larger. The steep slope along Hapeman Road is the foreset of the Elizaville Delta.

Beyond the foreset you enter the broad flat deeps of the lake or sea, and that is what we see at Elizaville. West of, and across the Hapeman Road is a flat landscape; it is the old floor of Glacial Lake Albany. The top of the delta is at about 280 feet, while Hapeman bottoms out at 220 feet. The lake was thus 60 feet deep.

Once, Hapeman Street marked the end of the Roeliff Jansen Kill, but that is not the case anymore, our journey is not yet complete.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”

“Old Man River”

Stories in Stone

Updated by Robert and Johanna Titus

We have been traveling down the length of the Roeliff Jansen Kill and we would like to continue on the third episode of this journey. Last time we explored the “drowned lands” of the Copake region. There we “saw” the Roeliff Jansen drainage basin as it was when ice age meltwater had drowned much of it. Now we continue our journey west and downstream as we pass through into the Taconic Mountains. These aren’t actually much more than hills, but they do exert a profound effect upon the very nature of the Roeliff Jansen Kill.

This week’s journey begins at the village of Ancram and finds us heading west on Route 7. We have left the swamps and marshes of the drowned lands behind, and what we see is something that is a much more conventional river valley. We are driving west through Gallatinville, and Spalding Furnace, two old towns with a lot of history. It’s a pretty landscape and it is easy not to notice the geological details. But there are things that we hope you will take note of.

At Ancram itself you will see bedrock in the stream. In fact, there is a pretty good ledge of it. That’s something we have not seen so far on our explorations of the Roeliff Jansen Kill. Back at the drowned lands we saw nothing in the way of bedrock. The whole upper part of the drainage basin is blanketed in ice age sediments. Much of it is sand and gravel, a lot of it is probably ice age lake sediment.

But from Ancram on west to Elizaville we will see, here and there along the stream banks, a number of nice ledges of bedrock. Sometimes you can see glimpses of the river from the highway, and you will look down into something of a bedrock canyon. At other times you will have to make a left turn and follow a side road down to the Roe-Jan. There you are, again, likely to be rewarded with another nice view of a bedrock.

These are the Taconic Hills, and they are made of very old units of rock. In our minds eyes we can travel to shallow and deep-water oceans that existed here hundreds of millions of years ago. Those ancient oceans accumulated masses of sediments which have, since then, hardened into rock. Mountain building events, which occurred 450, 375 and about 250 millions of years ago, have lifted these deposits to their current elevations.

We don’t know when the Roeliff Jansen Kill was first established, but it was likely a very long time ago. All rivers patiently erode away at the landscapes beneath them, and our Roe-Jan is no exception. And that gets us to the most important part of this column. This stretch of the stream is very, very old, many millions of years at the least.

Look left and right and, when the view is a good one, you will appreciate that a lot of erosion went into the creation of the valley here. And that erosion took a very long amount of time. Here is our hypothesis for this part of the river: Erosion of the valley between Ancram and Elizaville began millions and millions of years ago. During that long stretch of time the valley reached pretty much its present size and depth. Then, during the Ice Age, the whole region was buried in glaciers. After these glaciers melted the Roeliff Jansen Kill found its way back into its old channel. Back upstream, glacial sediments clogged the old valley, and the drowned lands came to be formed.

We are not yet done. Route 7 meets an intersection with Rt. 2, and you should follow Rt. 2 toward Elizaville. It seemed to us that the canyon grew deeper as we headed west. There were some very good bedrock exposures along the highway too. At Elizaville this stretch of the Roeliff Jansen Kill comes to an end. We have reached the western edge of the Taconics and are about to leave those hills. We will find a new geological province and see a different stretch of the Roeliff Jansen Kill. But that part of the journey will come next time.

Contact the authors at randjtitus@prodigy.net. Join their facebook page “The Catskill Geologist.”